Many computer devices take input from a keyboard. For example, a laptop computer has a display pivotably attached to a base comprising a keyboard. In addition to a keyboard, a computer device may also be attached to a mouse, or have a trackball or a touchpad for receiving further input. A touchpad detects touch by a user and converts this to an input signal. For example, a user may able to control a pointer shown on the display by moving their finger across a surface of the touchpad. Touch sensitive displays are also used by some computer devices, whereby a user is able to input instructions directly to the computer by touching the display.